The Immune System Has Protective Memory Cells, Researchers Discover

The immune system possesses a type of cell that can be activated by tissues within the body to remind the immune system not to attack our own molecules, cells and organs, UCSF researchers have discovered.

The discovery is likely to lead to new strategies for fighting a range of autoimmune diseases – in which the immune system attacks and harms specific molecules and cells within us – as well as for preventing transplant rejection, according to UCSF researchers who report their findings in the November 27 online edition of the journal Nature.

The cells tracked by the UCSF researchers circulate in the blood and are counterparts of the memory cells that help ward off microbial foes following vaccination orrepeated exposure to the same pathogen.

UCSF immunologist and chair of the Department of Pathology Abul Abbas, MBBS; Michael Rosenblum, MD, PhD, an assistant professor with the UCSF Department of Dermatology; and UCSF postdoctoral fellow Iris Gratz, PhD, used a mouse model of autoimmune disease to discover a role in immune system memory for cells called activated T regulatory cells.

They found that over time a tissue within the body – in this case, skin – defends itself from autoimmune attack by protectively activating a small fraction of T regulatory cells.

“It’s anovel concept – that tissues remember,” Abbas said. “Subsequent exposure to the same protein that elicited autoimmunity in that tissue may lead to less severe inflammatory disease.”

Autoimmune diseases, ranging from minor to severe, affect an estimated 50 million Americans. Immunologists had for decades blamed these diseases on faulty functioning of immune cells known as lymphocytes, including the cells that make antibodies that normally target foreign proteins found on infectious disease pathogens.

In autoimmune disease, lymphocytes may be directed against “self” proteins. In multiple sclerosis, for example, lymphocytes make antibodies that attack proteins in the insulating sheath that surrounds nerves. In lupus, antibodies attack DNA.

But in many cases autoimmune disease may involve abnormal responses by T regulatory cells, the UCSF researchers said. In recent years immunologists have come to recognize the important role that T regulatory cells normally play not only in ramping down an immune response during recovery from infection, but also inpreventing autoimmune responses.